Apparatus for separating vaporized volatile liquids from gaseous mixtures.



W. E. LUMMUS. APPARATUS FOR SEPARATING VAPORIZED VOLATILE LIQUIDS FROMGASEOUS MIXTURES.

APPLICATION FILED MAR.'I3. I9I2. 1 1 89 71 1, Patented July 4, 1916.

3 SHEETS-SHEET I.

$0. l/E/l/T 6705465 7214/ 74ft? sstsecs W. E. LUMMUS.

APPARATUS FOR SEPARATING VAPORIZED VOLATILE LIQUIDS FROM GASEOUSMIXTURES.

APPLICATION FILED MAR I8, 1912. 1,1

7 1 1 Patented July 4, 1916 3 SHEETS-SHEET 2.

WWWWW mwmm/wfl W. E. LUMMUS. APPARATUSFOR SEPARATING VAPORIZED VOLATILELIQUIDS FROM GASEOUS MIXTURES.

APPLICATION FILED MAR. 18. 1912. 1,1 89,? 1 1., Patented Jul 4, 1916.

3 SHEETS-SHEET 3.

UNITED STATES PATENT OFFICE.-

WALTER E. LUMMUS, 0F LYNN, MASSACHUSETTS.

APPARATUS FOR SEPARATING VAPORIZED VOLATILE LIQUIDS FROM GASEOUSMIXTURES.

1 H 93 1 L Specification of Letters Patent. Patented July 4 1916.

Application filed March 18, 1912. Serial No. 684,507. I

'[b all IP71 om it may concern:

Be it known that I, WALTER E. LUMMUS, a citizen of the United States,residing at Lynn, in. the county of Essex and State of Massachusetts,have invented certain new and useful Improvements in Apparatus forSeparating Vaporized Volatile Liquids from Gaseous Mixtures; and I dohereby declare the following to be a full, clear, and exact descriptionof the invention, such as will enable others skilled in the art to whichit appertains to make and use the same.

The present invention relates to apparatus for the separation bycondensation of the vapors of volatile liquids which are;

mixed with the so-call'ed permanent gases or gases which are liquefiablewith much more ditticulty than the vapors, of the volatile liquids whichit is sought to remove.

While the present invention may be employed to condense and separate themore condcnsable constituents from any vapor or gas mixture within thelimits of the power of the apparatus employed to liquefy sucheondensable constituents, the present invention is more particularlyapplicable for the separation of the volatile oils which exist in agaseous or vaporized condition in natural gas, for the removal of tarsand volatile constituents of the products of destructive distillationsuch as illuminating gas, wood gas and the like, and for the recovery ofthe volatile solvents used in applying coats of varnish or lacquer.

Natural gas. as it issues from the wells, usually contains more or lessgasolene, benzin and and similar volatile oils existing in a gaseouscondition, and which because of their volatile nature. cannot be readilyliquefied and separated from the relatively more permanent gases of thenatural gas mixture. As'tliese oils have a considerable commercialvalue, it is desirable to separate them in a liquid form from thenatural gas.

The. gaseous products of destructive distillation, such as thedestructive distillation of coal or wood, contain in a vaporizedcondition certain constituents which it may be desirable to removeeither for their own value or for the sake of purifying thegas.

Lacquers, varnishes and similar preparations are solutions of gums orsimilar substance dissolved in volatile solvents to permit ofapplication to the objects to be coated, and the value of the solventslost by evaporation in the drying of the objects to be coated, is withlarge establishments so cgnsiderable as to invite attentiveconsideration; for example, in the manufacture of coated clothsl,oilcloth and the like, the coa-tlng material is dissolved in the mixture ofamylacetate and gasolene. This solvent is of not inconsiderable valueand its recovery :1, material saving in the cost of operation of theestablishment.-

The object of the present invention is to produce an apparatus for usein condensing and separating the vapors of volatile liquids from gaseousmixtures in which said vapors are mlxed with other and less condensablegases. When a gas under a high pressure isexpanded in an expandingengine which transforms the heat energy of the expanding gas intomechanical energy, the gas is cooled to such a low temperature thatvapors which at all ordinary temperatures remain in a gaseous conditionare often condensed and even frozen in the engine, so that the engine isrendered very inefficient or even stopped. Such freezing of an expandingengine is often seen in tools driven by compressed air such as pneumaticdrills and the like.

Another object of the present invention is to produce an apparatus suchthat a gas under comparatively high pressure may be expanded withouthaving its temperature reduced to such a low point as to freeze itsvapor. This object is attained in the expanding engine shown in thepreferred embodiment of the present invention, by expanding thecompressed gas instages and allowing it to absorb heat between thestages of its expansion.

With the above objects in view, the present invention consists in theapparatus hereinafter described and particularly pointed out in theclaims.

While the present invention may be practised in condensing the leastvolatile constituents of a wide variety of gaseous mixtures and may beembodied in various kinds of apparatus particularly adapted to cope withthe conditions imposed by any particular gaseous mixture to be treated,yet, for the purpose of illustrating a complete operative structure, thepresent invention is illustrated and described as embodied in anapparatus for recovering the solvents used in coating cloth withlacquer, varnish and the like. It. is to be distinctly understo d,

and may be embodied in a wide variety of apparatus within the purview ofthe invention as defined in the claims.

While it is known that all of the formerly so-called permanent gases,such as oxygen, nitrogen, etc., are liquefiable under extreme conditionsof pressure and cold, and there is therefore no real physical line ofdemarcation between a vapor of a so-called 'volatile liquid and a gaswhich is relatively more difficult to liquefy, yet, for the purpose ofdistinguishing the constituents of a gaseous mixture, which on the onehand can be liquefied, from the constituents, which on the other handcannot be liquefied in an apparatus like that of the present invention,the term vapor is employed in thefollowing specification and claims todesignate the constituents of the mixture which are the vaporizedvolatile liquids sought to be condensed, and the term gas is employed todesignate the constituents of the mixture which are not sought to becondensed and which are discharged from the apparatus after the vaporhas been separated therefrom by condensation. The term gas-vapor mixtureis employed to define the mixture 'to be treated, which is composed ofthe vapor of the volatile liquids to be condensed, and the gas whichcannot be condensed in the apparatus. The gas-vapor mixture passes intothe apparatus, the vapor is separated by condensation and drawn off asliquid and the gas, which acts as an inert carrier for the vapor, isdischarged,

containing only traces of the vapor which it has been impossible orimpracticable to entirely separate from the carrier-gas. In thepreferred embodiment of the invention hereinafter specificallyillustrated and described, the evaporated solvent is the vapor to becondensed; and the air in which the solvent vapor is absorbed is the gasor carrier; the gas-vapor mixture is more specifically designated as theair-solvent mixture, or the carrier-solvent mixture.

' In the treatment of coated cloth air is preferably employed as thegaseous carrier for the solvent vapors so that in the following specificdescription of the preferred embodiment of the presentinvention the morespecific term air-solvent mixture is applied to mixture to be treated.It is under.- stood, however, that carrier gases other than air might beemployed, so that the terms carrier solvent mixture and gas vapormixture as used in the specification and claims are intended to definerespectively a mixture of a solvent in any gas and a mixture of thevapor of any liquid in any gas.

The preferred apparatus used for perpasses to the compressor.

forming my improved method is illustrated inthe accompanying drawings,in which;

Figures 1 and 2 are side elevations, partly in section, of'the left andright hand portions respectively of the apparatus and Fig. i is a planview of the portion illustrated in The line of juncture of the twoportions,

designated as the left and right hand portions, is marked a'm on each ofthe figures of the'drawings. In this connection attention is directed tothe fact that in Fig. 2 the floor line is lower than in Fig. 1, for thepurpose of greater convenience in illustrating the air compressor andits connections.

Precedent to a description of the method which forms the subject of thisinvention, the apparatus illustrated in the accompanying drawings willbe first briefly described and then described with greater particu-'larity and detail, and then the method will be more easily apprehendedthan if it were attempted in the first place to describe the method asan abstract series of acts performed upon the gaseous mixture to betreated.

The particular apparatus illustrated in drawings is intended for coatingcloth, such as oil cloth or imitation leather, for example.

In general, the operation of the apparatus is as follows: The cloth isintroduced into a coating machine and coated on one side with thecoating mixture. The cloth then asses through a drying tower in theopposlte direction to a current of previously used, purified and warmedair, to which the coated cloth is exposed for the purpose of drying thecoating. This is in fact a process of evaporating the coating solvent.The. air from the drying tower is then carried to a recuperatorcondenser, where it is. cooled vent is sometimes condensed and drawnoff.

From. the recuperator condenser the airsolvent mixture is led into awater cooled condenser in which more of the solvent vapor may becondensed, and in which the air-solvent mixture is cooled before it Theliquid solvent collected in the cooler condenser, together with theliquid from the recuperator condenser,'is cooled in the lower part ofthe cooler condenser, before it is drawn off to the solvent storage.tank. From the cooler condenser the air-solventmixture which containsthe solventvapors which were not condensed and liquefied in the coolercondenser is led to an air compressor where it is compressed in twostages. Thev compressed mixture discharged from the low pressurecylinder of theair compressor is led through two condensers, forconvenience designated as the low stage pressure cooler and the lowstage pressure refrigerator respectively, before it.enters the highpressure cylinder 'of the condenser. cooler is a water cooled condenserand absorbs va large amount ofheat from the mixture before it passes tothe pressure refrigerator, The refrigerator is a condenser cooled by thecold expanded purified air exhausted from the low pressure cylinder ofthe expanding engine hereinafter described and cools the mixture to a.low temperature.

before it is further compressed in the high pressure cylinder of thecompressor. From the high pressure cylinder of the compressor themixture passes through two condensers similar to the low stage pressurecooler and the low stage pressure refrigerator, and which forconvenience, of nomenclature .are spoken of as the high stage pressurecooler and high stage pressure refrigerator. The high stage pressurecooler, like the low stage pressure cooler, is a water cooled condenser,and absorbs a large part of the heat from the compressed mixturedischarged from the high-pressure cylinder before it passes into thehigh-stage pressure refrigerator. The high-stage pressure refrigeratoris cooled by the cold expanded purified gas exhausted from the highpressure cylinder of the expanding engine, and the mixture as dischargedfrom the pressure refrigerator is cooled to a low temperature. The coldcompressed mixture as it leaves the high-stage pressure refrigeratorstill contains more or less of the solvent which remains in suspensionin the air in the form of fog or mist. The air with the entrained vaporfog is led from the highstage pressure refrigerator to a washing columnor 'tower in which the suspended vapor particles are washed from the airand liquefied. The solvent liquefied in the pressure coolers, pressurerefrigerators and washing column is drained off through suitable trapsto the solvent storage tank. This washing operation is the final step inthe condensation and liquefaction of the solvent vapor, and removes allof the eliminable solvent from the air, so that the air as dischargedfrom the washing tower is clean or desaturated, containing only a verysmall per cent. of the total solvent which it absorbs in the dryingtower. The clean purified air from the washing column contains so littlesolvent that any further attempt at recovery is impracticable. However,the air discharged from the washing column is very cold and is under acomparatively high pressure, so that if .it is expanded adiabatically itwill not only furnish power to assist in driving the air compressor, butis also particularly adapted after expansion to be used as therefrigerating medium to cool the air-solvent mixture in the pressurerefrigerators. With these objects in view, the clean or desaturated airfromthe washing The pressure column led to the high pressure cylinder ofa two stage expanding engine in which it is adiabatically expanded. Thisexpansion reduces. the temperature 'of the air far below its temperaturein the washing column.

The cold expanded air is discharged from tlIG lIlgl1-PI'GSSUI'Bexpanding cylinder into the high-stage pressure refrigerator, where itacts as the cooling medium. The partially expanded air, in passingthrough the highstage pressure refrigerator, absorbs heat from theair-solvent mixture, and to still further expand and cool the air it 'isled from the high-stage pressure refrigerator to the second orlow-pressure cylinder of the expanding engine in which its pressure isreduced to about atmospheric pressure. The cold expanded air from thelow-pressure expanding cylinder is led into the low-stage pressurerefrigerator where, acting as the refrigerating medium, it absorbs heatfrom the air-solvent mixture. From the lowpressure refrigerator theexpanded air is led through the recuperator condenser where it absorbsstill more heat from the warm airsolvent mixture coming from the dryingtower. From the recuperator condenser the desaturated or purified air isled through a heater where it is heated to the proper temperature, andreintroduced into the drying tower. The heated purified air absorbs thesolvent vapors in the drying tower, and again passes through the abovedescribed cycle of processes.

As illustrated, the purified or desaturated air coming from the washingcolumn through the two expanders and the condensers, in which it acts asthe cooling medium, still retains traces of solvent vapor which it ispractically impossible to entirely remove. By returning the air to thedrying tower this condensed solvent is conserved within the apparatus.Of course if the uncondensed solvent is not worth saving, or if itspresence materially reduces the absorptive power of the air when reintroduced into the drying tower, the air after leaving the recuperatorcondenser may be discharged into a fine or chlmney, and a 'The cloth 5enters the tower at the bottom,

passes over the roller 6 and down on the 1 other side ofthe tower outunder the roller 7. The drying tower is divided by a partition 8, whichextends nearly from top to bottom and is provided with weather-striplikeclosure at the rollers G and 3 at the top and bottom. The entrance andthe exit of the cloth are guarded by flexible strips 9 and 10 and theidle roller 11 which stops up spaces between the cloth where it entersand where it leaves the coating and drying apparatus. A knife or slicker12 regulates and distributes the coating mixture as desired. Thepartition 8 extends completely across between opposite sides of thedrying tower. as do also the coating and guiding rollers which arejournaled on each sidev of the tower. The pure air is heated in a heater15 to the temperature which is found to be best for drying theparticular coating material used, and is introduced into the dryingtower through the inlet 16 located near the lower end of the tower. Thedrying tower is about 30'feet in height. The inlet 16 for the air issubstantially the width of the tower, as is also the outlet 17, in orderthat the air may be distributed over the entire width of the cloth beingdried.

The direction of the flow of air through the drying tower is counter tothat of the movement of the cloth. This contributes to the etliciency ofthe drying tower, since the pure air from the heater is first passedover that portion of the cloth which is nearly dried of solvent, andthen passes along over portions of the cloth from which less and less ofthe solvent has been evaporated, until the air as it is dischargedthrough the outlet 17 passes over the freshly coated cloth coming upfrom the trough 1. The temperature of the air as it emerges from theoutlet 17 carrying the solvent vapors with it is reduced somewhat belowthe temperature at whichit was introduced through the inlet 16, thereduction in temperature being principally due to the heat absorbed bythe evaporation of the liquid solvent from the coating. This air-solventmixture is led through the pipe 20 to the recuperator condenser-21, andis discharged into the intertubular space thereof. The recuperatorcondenser comprises a cylindrical shell about 12 inches in diameterhaving two partitions 22 and 23 at its ends connected by a plurality ofsmall condenser tubes 24. A relatively large heat absorbing surface isthus exposed to the air solvent mixture by employing a large number ofsmall tubes arranged closely together. A series of bafiie plates 25 ispro vided, and the plates are placed nearer together toward the righthand end of the condenser because the volume of the air solvent mixturediminishes as its temperature is reduced by contact with the coolingpipes. Any solvent which is condensed and liquefied by the cooling ofthe air-solvent mixture in the recuperator condenser is drawn offthrough a drain pipe 26 connected at a number of points along the bottomof the recuperator condenser and discharged into the bottom of theinter-tubular space of the cooler condenser. A trap 27'is provided inthe drain pipe 26 to prevent the air passing through it. The coolingmedium for the recuperator condenser is the cooled returning purifiedair on its way to the drying tower. It is to be observed'that the coolpure air passes through the recuperator condenser to the left, while theair-solvent mixture passing around the tubes moves in a generaldirection toward the right, or in counter-current fashion to themovement of the cold air, which conduces to the most eflicient operationof the condenser, so that the air-solvent mixture discharged at theright-hand end of the recuperator condenser is cooled and the airdischarged at the lefthand end of the recuperator condenser is heated.It is because of this interchange of heat between the air and theair-solvent mixture that the term recuperator condenser has been chosenas a name to designate this particular condenser.

The air-solvent mixture is led from the recuperator condenser through apipe 30 to the cooler condenser 31. The cooler condenser is cooled by astream of water flowing upward through its tubes in c'ountercurrent tothe air-solvent mixture, which flows downward through the inter-tubularspace of this condenser. The cooler condenser is shown arrangedvertically, and is of smaller diameter than the recuperator condenser,but in other respects is similar to it, and comprises a plurality ofsmall reserved for the cooling of the condensed solvent in partdischarged through the pipe 26 from the recuperator condenser and inpart condensed and collected inthe upper part of the cooler condenser.The distances between the battle plates are decreased from the toptoward the bottom, as shown. The distances between the loaflie platesfrom the top to the bottom are reduced like the arrangement of thebaffle plates in the recuperator condenser. The temperature of theair-solvent mixture isreduced in the cooler condenser to about thetemperature of the condenser water, and the air-solvent mixture isdischarged from the cooler condenser through the pipe 33 which opensfrom the side of the cooler condenser a little above the level of thecondensed solvent at the bottom. The condenser water is led into thebottom of the cooler condenser through a valve connection 34 from thewater supply pipe .35, and is discharged from the top of the coolercondenser into the water discharge pipe 37.

The solvent collected in the recuperator condenser 21 and drained intothe bottom 'of the cooler condenser through the pipe 26,

liquid respectively, for the purpose of pre-f venting syphonic action.

The air solvent mixture coming from the cooler condenser is atatmospheric pressure and at a temperature a little above the temperatureof the condenser water, and therefore contains solvent which is notcondensable at this pressure and temperature. The air-solvent mixturepassing through the pipe 33 from the cooler condenser is discharged intothe low-pressure cylinder 50 of a two-stage air compressor, in which itis compressed to a pressure which is'determined by the character of theair-solvent mixture. As will later appear, the greater the pressureobtained by the compressor, the greater will-be the cooling of theair-solvent mixture in the pressure refrigerators, but there is acertain upper limit beyond which the compression must not go, because ifan attempt be made to compress a solvent mixture having a 'com-.

paratively low flash point or ignition tem: perature to too great apressure in a single stage of the compressor, the mixture may take fireand explode. For these reasons it is impossible to state any precisepressure to which the mixture is compressed, as it must be determined bythe character of the solvent. The two-stage air compressor comprises thelow and high pressure cylinders 50 and 52 respectively, placed intandemand having their common piston rod 54 driven by the crank 56 ofthe driving shaft 58 through the pit-man 57 The power'to turn thedriving shaft is furnished partly by an electric motor 60, and partly byan expanding engine which comprises the low and high-pressure cylinders62 and 64 respectively arranged in tandem and having their common pistonrod 66 connected by a pitman 68 to the crank 7 0 of the driving shaft58. A comparatively heavy fly wheel 72 is provided Ito store power, andto keep the air compressor and the expanding en gine running evenly. Thepower to drive the expanding engine is furnished by the cold compressedand purified air, as will be hereinafter more fully set forth. Theairsolvent mixture compressed in the low-pressure cylinder 50 is ledthrough a pipe 80 into the top of a condenser 82. A safety valve 81 inthe pipe 80 is provided as a precaution against excessive pressures.

his condenser, for convenience, has been designated as the low-stagepressure cooler, since in it the compressed air-solvent mixture from thelow-pressure condenser-cylinder 50 is cooled. The air-solvent mixturedischarged from the low pressure cylinder 50 into the pipe 80 may haveany temperature up to its flash point.

The condenser 82 is constructed similar to the recuperator condenser andcooler condenser having a large number of condensing pipes therein, andhaving bafile plates in the intertubular space to direct the air-solventmixture in a tortuous passage of the intertubular space of thecondenser. The airsolvent mixture enters at the top of the pressurecooler and passes downward through "the intertubular space. The pressure cooler is cooled by water which passes into the bottom of thecondenser through a valve 84 from the water supply pipe 35 and isdischarged through a valve to the water discharge pipe 37. Theair-solvent mixture passing through the low stage pressure cooler 82 isunder the pressure given it in the loW pressure cylinder of'thecompressor and more of the solvent vapor will be condensed and liquefiedbecause an increase in pressure is one of the factors causingcondensation of a vapor. The solvent condensed and collected in the lowstage pres sure cooler is drawn off through a trapped drain pipe 94' tothe trap 96 and thence through the pipe 98 to the solvent storage tank40. Since liquid solvent in the pipe 94 is under pressure it isnecessary to reduce its pressure to nearly that of the atmosphere beforeit is discharged into the pipe 98 leading to the tank 40. For thispurpose the trap 96 is constructed to allow the passage of the liquidsolvent and to discharge it at about atmospheric pressure into mixtureis discharged from the bottom of the low stage pressure cooler 82through a pipe 88 which leadsit into the top of another condenser "whichhas for .convenience been designatedv as the low. stage pressure--refrigerator,,because in this condenser the air-solvent mixture:compressed 111 the low-' pressure. cylinder ,-50;and cooled nthe lowstagei pressure cooler 82 tea temperature about that ofthe condenserwater is supercooled. The drop in temperature in the purified gas causedby its expansion in the expanding engine is 'sufiicient to maintain thetemperature of the two pressure refrigerators at a temperature below 0centigrade and the term low temperature as hereinafter used in thespecification and claims is intended to define a temperature below 0centigrade. The expression supercool as used in the specification andclaims is intended to define the step of the operations in which thegas-vapor mixture,

already cooled in one condenser, is cooled still further by being passedinto a second condenser maintained at a lower temperature than saidfirst condenser, and, unless otherwise qualified, the supercooling isnot necessarily to a temperature below 0 cen-.

tigrade. The low stage pressure refrig-' erator is constructed similarto the previously mentioned condensers, having a number of condensertubes and baflle plates. The air-solvent mixture passes downwardlythrough the intertubularspace of the low stage pressure refrigerator,and is discharged through an inverted U-shapedconnection 92 into thepipe 93 which leads to the high pressure cylinder 52 of the compressor.The pressure refrigerator 90' is cooled to a low temperature by theexpanded air coming from the low stage -expanding cylinder 62, so thatin the low stage pressure refrigerator 90 the air-solvent mixture issubjected both to pressure and to low temperature. Both of these factorscombine to condense still more of the uncondensed solvent vapor. Thesolvent vapor condensed and collected in the pressure refrigerator 90 isdrained off-through a pipe 100 into the balance float trap 96, andthence to the solvent storage tank.

The partially compressed air-solvent mixture. coming from the low-stagepressure refrigerator through the pipe 92 is given its final compressionin the high-pressure cylinder 52 ofthe air compressor. The degree ofcompression to which the air-solvent mixture is subjected in the highpressure cylinder will be determined, like that in the low pressurecylinder, by the degree of refrigeration desired and the flash point ofthe particular air-solvent mixture which is to be treated by theapparatus. While, for the above reasons, no fixed rule can be stated asto the degree of compression, yet in the treatment of certain solventsthe pressure of the final stage of compression may be carried to overone hundred pounds per square inch. The air-solvent mixture by itscompression in the high pressure cylinder 52 is raised in temperatureand after it is discharged from the high pressure cylinder it is ledthrough a pipe 110 to a water cooled condenser 112 which has beendesignated for convenience as the high-Sta e pressure cooler in which alarge part of t e heat of the air-solvent mixture is absorbed by thecondenser water. A safety valve 113 is provided to guard againstexcessive pressure in this part of the apparatus. The high-stagepressure cooler is similar in construction to the low-stage pressurecooler 82 except that it may be made somewhat smaller since the volumeof the air-solvent mixture is reduced by compression and condensationand the condenser should be made of stronger construction to withstandthe increased pressure. The condenser water enters through a valve 114from the water supply pipe 35 into the bottom of the con;

denser and is discharged from the top of p the condenser through a pipe118 into the water outlet pipe 37. The solvent condensed and collectedin the high-stage pressure cooler 112 is led through a trapped drainpipe 122 to a balance float trap 124 I and thence through the pipe 98 tothe solvent storage tank 40. The cooled compressed air-solvent mixturefrom the highstage pressure cooler 112 passes through a pipe 126 to thehigh-stage pressure refrigerator 130 in which it is supercooled to a lowtemperature by the returning purified.

air from the exhaust of the high pressure cylinder 64 of the expandingengine. The high-stage pressure refrigerator 130 is similar inconstruction to the low-stage pressure refrigerator 90 except that itmay be smaller and should be of stronger construction because of thedecreased volume and increased pressure of the air solvent mixture.Incidentally it is to be noted that, since the cold air in the condensertubes of*the high-stage pressure refrigerator is under pressure, thewalls of the condenser tubes may be made thinner than would be possiblein case the cooling medium in the condenser tubes was not underpressure. Also by having the most highly compressed air-solvent mixturecooled by the most highly compressed purified air and the lesscompressed mixture cooled by the less compressed, or, in other words, byutilizing the expanded air after each downward stage of expansion tocool the compressed air-solvent mixture after the succeeding upwardstages of compression taken in their inverse order, both the mixture andthe air pamages of 'the high stage pressure refrigoperation; In all ofthe pressure condensers 82,90, 112, 130, a large number of condensingpipes are used and thewalls of these pipes are made as thin as isconsistent with safety so as to allow the greatest possible exchange ofheat between the cooling medium and the mixture to be condensed. Theair-solvent mixture (after passing downward through the intertubularcolumn consists of a cylindrical shell having a number of decks ordiaphragms 140 extending across it. From the decks 140, riser pipes 142extend upwardly and are covered by caps or hoods 144 which extend 'jectabove the decks.

down over the riser pipes. Drain pipes 146 extend through the decks toconduct the condensed liquid downwardly. The depth of the liquid on thedecks 140 is determined by the distance that the overflow pipes pro-Each overflow pipe extends downwardly to nearly the top of the deckbelow so that the bottom of each of the overflow pipes is sealed by theliquid standing on thedeck below to prevent the upward passage of theair through the overflow pipes.- Y

A dam 147 extends across one side of the bottom ofvthe Washing column toretain, liquid to seal the lower end of the overflow pipe of thelowermost deck. The top deck of the washing column 138 is supplied withthe liquid solvent collected in the high-stage pressure refrigeratorthrough the drain pi e 150. The condensed solvent collects on the decks140 so that the air-solvent mixture which passes upward through thewashing column 138 bubbles out beneath the edges of the hoods 144 and athorough washing of the air-solvent mixture by the liquid solvent isassured. The air-solvent mixture coming from the high-stage pressurerefrigerator 130 is at a high pressure and a low temperature so thatpractically all of the solvent is condensed. However, some of thecondensed solvent usually persists in the form of a mist or fog and itis for the purpose of recovering this mist or fog that the air-solventmixture is subjected to the repeated washings in the washing column 138.While any form of cap or hood 144 which will insure an even distributionof the vapor around its edge may be used, the form of cap or hooddisclosed in the patent to Walter E. Lummus for boiling caps, No.973,795, October25, 1910, is preferred. The washing column 138 is not anabsolutely necessary element of the apparatus but is a valuable adjunctor addition employed to secure a more thorough removal of the solvent.

The air-solvent mixture discharged at the top of the washing column 138isvery cold, under a high pressure and is desaturated of the eliminablesolvent. The air in this condition has been spoken of in the general description as the returning clean or purified air. This clean coldcompressed air is led I y from the washing column 138 through the pipe152 to the high pressure cylinder .64 of the expanding engine in whichit is expanded adigbatically, the heat being expended in the forin ofmechanical energy to turn the drivmg shaft 58 and assist the motor 60.The

partially expanded air, which is very cold, 4

being reduced by adiabatic expansionto a temperature considerably lowerthan the temperature at which it was introduced into. the expandingcylinder 64, is led through a pipe 154 to the high-stage pressurerefrigerator 130 where it acts as the coolingmedium. The air passesupwardly through the tubes of the pressure refrigerator, is dischargedat the top and passes down through a pipe 156 to the low pressurecylinder 62 of the expanding engine. In the cylinder 62 the air isadiabatically expanded to a pressure-about that of the atmosphere and isled from the exhaust of the cylinder 62 through a pipe 160 to the bottomof the low-stage pressure refrigerator 90 through the condensing tubesof which it passes upwardly and is discharged intothe pipe 162. Thereturning air as it passes through the high-stage pressure refrigerator130 absorbs heat from the air-solvent mixture so that, although stillcomparatively "cold, it is warmer than when exhausted from the highpressure cylinder 64. The adiabatic expansion in the cylinder 62 of theair coming from the high-stage pressure refrigerator 130 again cools itto a low temperature so that when it passes through the condenser tubesof the low-stage pressure refrigerator 90 it is a very cold coolingmedium. The expanded air dis- \charged into the pipe'162 is ledthroughit to the recuperator condenser 21 through the condenser tubes 24passing from right to left. In the recuperator condenser there is,

as before mentioned, an interchange of heat between the warm alr-solventmixture from the drying tower and the cool returning purified air sothat the returning air absorbs considerable heat and is'led from therecuperator condenser 21 through a pipe 17 O to the heater 15 where itis heated still more before being introduced into the drying tower.

In the above specific description, the apparatus has been describedfollowing they closed circuit of the circulation of the air from thedrying tower through the-various condensers and compressors to thewashing column and then back through the various expanders andcondensers to the ,drying tower again. During the operations upon theair-solvent mixture up to the time the air is discharged from thewashing column the air acts both as a motive fluid for the expandingengine and as a refrigerating medium for the two pressure refrigeratorsand the-recuperator condenser.

To more readily present the essential features of the present invention,the drawings are shown as illustrating the apparatus in a diagrammaticform rather than illustrating the exact details of the mechanicalconstruction. For example, the connections with the cylinders of the aincompressor and the expanding engine are. indicated diagrammatically andthe various slide valves and their actuating mechanism which arenecessarily involved in the use of such compressors and expandingengines are not shown. Nevertheless the operation of the compressor andthe expanding engine will be readily understood by those skilled in theart. While a two stage compressor and a two stage expanding engine areillustrated, a single stage compressor and expanding engine orcompressorsand expanding engines of more than two stages may be useddepending upon the circumstances. However, there are certain advantagesattained by compression and ex pansion in a plurality of stages. Viewingthe compression as an operation alone, compression in a plurality ofstages with cooling between stages possesses the important advantagesthat a high final pressure can be attained without raising thetemperature of the gas-vapor mixture dangerously near its flash point atany of the series of stages of compression, and that less power will beconsumed because the average temperature of the gas during theentirecompressing op-' eration is kept lower than the averagetemperature could be kept if the entire compression took place in asingle stage. Viewing the compression and expansion as interdependentand cooperating operations, the plurality of stages of compression andexpansion allows a more gradual and economical interchange of heat totake place between the compressed gas-vapor mixture and the expandedgas. As illustrated, the warm gasvapor mixture from the compressorcylinders can be cooled in water cooled condenser and then supercooledby the expanded gas in another condenser. By extracting the heat of thegas-vapor mixture in a number of stages each stage consisting of theabsorption of heat by some external cooling medium such as water and thefurther absorption of heat by the expanded gas, a very panding engine bycausing condensation and freezing in the engine of vapors entrained inthe gas, but also allows the expanding gas to do a greater amount ofmechanical'work thaii if it were expanded in a single stage. If a singlestage expansion were, to take place with a gas under high pressure, thesudden cooling by expansion might be so great as to freeze less volatilevapors and clog the expanding engine, but' by expanding by stages thecold expanded gas from one stage absorbs enough heat before itsexpansion'in the next lower stage so that the temperature during anystage of expanding does not drop so lowcas to interfere with themechanical operation of the expanding engine.

. In an apparatus like. that illustrated it would probably be impossibleto expand the cold compressed gas in a single stage with.- out causingsuch a very low temperature as to freeze in the engine cylinder vaporsmore volatile than those condensable in the condensers. The absorptionof heat by the cold gas exhausted from one cylinder before it enters thecylinder of the next lower stage increases the ability of the gas to domechanical work in the cylinder of the next lower stage and thereforethe expansion by stages with absorption of heat between the stagesproduces more mechanical work than the expansion of the same-gas in asingle stage. Where the-principal object of the expansion is, like thatof the illustrated apparatus, a thermal one, namely the cooling for thepurposes of condensation of a gasvapor mixture, the only heat absorbedby the expanded gas is taken from the gas-vapor mixture, but when theprincipal object of the expansion of a gas is a mechanical one, namely,the conversion into mechanical motion of the energy to be derived from agiven volume of compressed gas, the gas between its stages of expansionmight be aling the entire operation of expanding the gas, the greaterwill be the amount of mechanical work .done by the expanding engine.This feature of the invention, namely expansion by stages, may beequally well employed in any kind of apparatus where a highly compressedgas, such ascompressed air, is expanded and does mechanical work.

While in the illustrated embodiment the vapor-gas mixture, morespecifically desig-.

nated as the air-solvent mixture, is led through four different types ofcondensers, viz., the recuperator condenser, the cooler condenser andthe pressure coolers and pressure refrigerators, the employment of allof these types of condensers is not essential to all forms of apparatusin which the present invention may be embodied and one or more of thecondensers may be omitted within the purview of the invention in itsbroader aspects For example, in an apparatus for l quefying the volatileoils from natural gas, since the gas as it issues from the well is cool,the condensers like the recuperator-con denser and cooler condenser maywith ad vantage be dispensed with. Neither is the employment ofcondensers of the exact type illustrated deemed essential; thereforewhen the word condenser alone is used in the specification and claims,it is, intended to be understood in its broad sense and is not intendedto define any particular type of the condensers illustrated. Moreover,condensers like the pressure refrigerators as illustrated, in whichthere is a direct transfer of heat through the tube walls between the"gas-vapor mixture and the expanded gas, are not essential to thetransfer of heat from the gas-vapor mixture to the expanded gas,

and the employment of some circulating heat carrying medium such as abrine which is cooled in a separate container by the expanded gas and ispiped into the refrigerator condenser to act as the refrigerating mediumfor the gas-vapor mixture, is within the purview of the invention.

The statement in the specification and claims that the expanded gas isutilized for cooling the compressed gas-vapor mixture is intended toapply to a method or apparatus in which the expanded gas is used as thedirect refrigerating medium for the gas-vapor mixture or in which theheat from the gasvapor mixture is transferred to the expanded gas bymeans of some intermediate heat transferring medium such as brine.Neither is it essential, in the present invention viewed in some of itsbroader aspects, that the brine be cooled by the expanded gas asit maybe cooled by some refrigerating apparatus entirely independent andseparate from the means for expanding the compressed gas.

Some gas-vapor mixtures which are to be treated may contain, vapors"which when treated alone cannot be condensed (from the mixture) at thepressures and temperatures within the practicable attainments of theapparatus. Many of these vapors may, however, be condensedif they aremixed with the vapor of some more readily condensable substance such ashigh boiling oils and the like which can be condensed in the apparatusand which act in the nature of catalytic agents to assist in thecondensation of the more diflicultly condensable vapors. In such .casescondensation assisting substances such as high boiling oils and thelike'may be added by injection or otherwise to the gasvapor, mixture tofacilitate "the recovery of f the said more volatile constituentsthereof.

As the gas-vapor mixture passes through the various condensers'andrefrigerators, the volatile constituents thereof are successivelycondensed and removed the: order of their n condensation of the variousvolatile liquids forming the vapor may be had.

As illustrated in the preferred embodiment of the present invention, theheat absorbing capacity of the expanded purified gas is distributed in aplurality. of refrigerators, each being arranged to supercool thecompressed gas-vapor mixture after the successive stages of compression,and, as above pointed out, a selective condensation of the volatileconstituents of the gas-vapor mixture takes place. Under certaincircumstances it may be desirable instead of utilizing the heatabsorbing capacity of the purified expanded gas in a number ofrefrigerators, to utilize the entire heat absorbing capacity in a singlerefrigerator and thereby Y to attain the lowest possible temperature.

When it is desired to utilize the entire heat absorbing capacity of theexpanded gas in a single refrigerator, the purified compressed gas isexpanded, either in a single stage expanding engine or in a multiplestage expanding engine, in which the gas is led directly from oneexpanding cylinder to another without the opportunity to absorb heatbetween its successive expansions, and the expanded gas is led through asingle refrig-v erator corresponding to the high stage pres surerefrigerator 130 of the drawings in which the compressed gas-vapormixture is subjected to the lowest temperature attainable by expandingthe purified gas. In such a modified form of apparatus the gasvapormixture is subjected to a single refrigeration which condenses andremoves all volatile constituents not condensable at the temperature ofthe condenser water, as contrasted with the multiple stage refrigerationand selective condensation of such volatile constituents which takesplace when the compressed gas-vapor mixture is passed successivelythrough two or more refrigerators cooled by the expanded gas. It will beevident that in this manner a much lower temperature can be attained andthat vapors can be condensed which might be too volatile to be condensedwhen the heat absorbing capacity of the expanded gas is distributed in anumber of separate refrigerators.

that any'form' of expanding engine may be employed; for instance, thepurified air might be expanded through a turbine which would extractpart of the heat in the form of mechanical energy or the expandedpurified air might be cooled by being expanded through'a 'needle'valveor fine opening or described and illustrated, have been indiopenings tocause a reduction in the temperature due to what is known as the Joule-Thomson effect of expanding a, gas through a fine opening or porousplug. However, since an adiabatic expansion causes a much greater dropin temperature than the expansion through a fine opening due to the Joule-Thomson efl'ect, an expansion adiabatic so far as practicable ispreferred. Of course the expansion through any sort of engine is notperfectly adiabatlc but the term adiabatic as used in'the specificationand claims is to be understood as defining an expansion in which more orless of the heat energy is transformed into mechanical energy dependingupon the efliciency of the expanding engine. Wh1le from the point ofview of the conservation of mechanical energy within the apparatus it ispreferable, as illustrated, to utilize the mechanical energy of theexpanding engine to drive the compressor, yet the mechanical energy ofthe expanding engine might be otherwise utilized or even thrown awaywithout affecting the thermal relation of the expanding engine to therest of the apparatus.

Of course if the gas-vapor mixture to be treated is already underpressure, the compressor 'can'be omitted and the gas-vapor mixture bepassed directly, Without further compression, into a condenser orcondensers and then expanded, and the expanded purified gas utilized forcooling the condenser or one of the condensers.

While some of the modifications, which might be made in the apparatusspecifically cated, many other changes or omissions may be made in thearrangement of said apparatus within the purview of the invention asdefined in the following claims 1. An apparatus for separating vaporizedvolatile liquids from gaseous mixtures having, in combination, means forcompressing the gas-vapor mixture, means for cooling the compressedgas-vapor mixture to condense the vapors, and means for washing thecooled compressed gas-vapor mixture, substantially asrdescribed.

2. An apparatus for separating vaporized volatile liquids from gaseousmixtures having, in combination, means for compressing the gas-vapormixture, means for cooling the gas-vapor mixture to a low temperature tocondense the vapors, and means for washing the cooled compressedgas-vapor mixture, substantially as described.-

3. An apparatus for separating vaporized volatile liquids from gaseousmixtures having, in combination, means for compressing the gas-vapormixture, means for cooling the compressed gas-vapor mixture, means forwashing the cooled compressed gasvapor mixture, and means for expandingthe washed and purified gas, theexpanded gas being utilized to absorbthe heat taken from the compressed gas-vapor mixture by the said coolingmeans, substantially as described.

4. An apparatus for separating vaporized volatile liquids from gaseousmixtures hav- 5. An apparatus for separating vaporized volatile liquidsfrom gaseous mixtures having, in combination, means for compressing thegas vapor mixture, means for cooling the gas-vapor mixture, means forsupercooling the cooled gas vapor mixture to a low temperature tocondense the vapors, and means for expanding the purified gas inlaplurality of stages, the expanded purified gas being utilized toabsorb'the heat taken from the gas-vapor mixture by the said'supercooling.

means, substantially as described.

6. Anapparatus for separating vaporized volatile liquids from gaseousmixtures having, in combination, 'means for compressing the gas-vapormixture in a plurality of stages, means for cooling the compressedgas-vapor mixture after each stageof compression, and means forexpanding the purified gas in a plurality of stages, the expandedpurified gas after the several stages of expansion being utilized toabsorb the heat taken from the compressed gas-vapor mixture by the saidcooling means after the several stages of compression, substantially asdescribed.

7. An apparatus for separating vaporized volatile liquids from gaseous.mixtures having, in combination, means for compressing the gas-vapormixture in a plurality of stages, means for cooling the compressedgas-vapor mixture after each stage to condense the vapors, and means forexpanding the purified gas in a plurality of stages equal in number tothe stages of compres-- sion, the expanded purified gas being utilizedafter each succeeding upward step in stages, means for cooling thecompressed. gas-vapor mixture'after each stage of compression, means forsupercooling the compressed gas-vapor mi ture after each coolingoperation to condense the vapors, and

as being utilizedto absorb the heat taken rom the compressedgas-vapormixture by the said supercooling means, substantially as 7described.

9. An apparatus for separating vaporized volatile liquids from gaseousmixtures having, in combination, means for compressing the gas-vapormixture, means for cooling the compressed gas-vapor "mixture. after each7 stage of compression, means for supercooling the compressed gas-vapormixture to a low temperature after each of said coolingoperations tocondense the vapors, and means for adiabaticallyexpanding'the purifiedgas in a plurality of stages, the expanded purified gas being utilizedto absorb the heattaken rom the compressed gas-vapor mixture by "saidsupercooling means, substantially as described.

10. An apparatus for recovering solvents having, in combination, acollector having a pure-carrier inlet and a carrier-solvent mixtureoutlet, in which the solvent-containing material-is exposed to theaction of the car rier which absorbs the solvent from thesolvent-containingmaterial, a cooler in which the carrier-solventmixture is cooled, a compressor, connections between said condenser andthe compressor, a condenser 1n WhlCh' the compressed carrier-solventmixture is cooled to a low temperature to condense the solvent,connections between the compressor and saidsecond condenser, anexpanding englne, connections betweensald second condenser and theexpanding engine, and connections between the expanding engine and thepure-carrier inlet of the collector for returning the purifiedcarrienfor reuse, the expanded purified carrierbeing utilized forcooling the compressed carrier-solvent mixture, substantially asdescribed. a

'11. An apparatus for separating 'vaporized volatile liquids fromgaseous m xtures,

having, in combination, means for compressing the gas vapor mixture,means for'cooling the compressed gas vapor mixture to a low temperatureto condense and separate the vapors, and means to liquefy and absorb thevapor condensate in the form of a fog in the compressed gas vapormixture, substantially as described.

12. An apparatus for separatmgvapor-v ized volatile liquids from gaseousmixtures,

having, in combination, means for compressing the gas vapor mixture,means for cool- .ing the compressed gas vapor mixture to a lowtemperature to condense the vapors, and means to pass the compressedcooled gas vapor mixture through a'condensate solution ofa ized volatileliquids from gaseous mixtures,

having, in combination,"means for compressing the gas vapor mixture instages, means for cooling the gas vapor mixture at the stages tocondense the vapors and cooling the compressed mixture to a lowtemperature, and means to wash the cooled compressed gas va or mixtureto remove the condensate in t e form of a fog, substantially asdescribed.

I 14. An apparatus for separating vaporized volatile liquids fromgaseous mixtures, having, in combination, means for compresslng the gasvapor mixture, means for cooling the. compressed gas vapor mixture tocondense vapors, means to expand the compressed urified gas againstpistons in a plurality 0 stages to do work and utilize the vexpanded gasto absorb heat taken fromthe and condensing the gas vapor mixture beforecompression thereof to remove the easily condensable portion'of the gas,means for compressing the residue of the gas vapor mixture, and meansfor supercooling the compressed residue to separate further vaa pors,substantially as described. 16. An ized volatile liquids from gaseousmixtures,

ing gas vapor mixture in a' pluralit of stages, means for cooling thecompresse gas vapor mixture at each stage, means to refrigerate the gasat each stage to condense vapors, and means to collect the condensedvapors from the difl'erent stages, substantially as described.

17. An apparatus for separating vaporized volatilevliquids from gaseousmixtures, having, in combination, means for compressing the gas va ormixture in a plurality of stages, means or cooling the compressed gas ateach stage to condense vapors therefrom, means to expand the compressedpurified gas in a plurality of stages, and means for conv apparatus forseparating vapor 10. having, in cpmbinatiommeans for compress-

